A certain number of medicaments formulated in powder form are orally inhaled by way of an inhaler having a mouthpiece for insertion into the user's mouth. These are in particular medicaments for asthma and other pulmonary diseases. A difficulty is that sometimes the patient has problems in synchronizing his inhalation with the manual operation of the distributor part of the inhaler so that inhalation occurs at the time when the powder is expelled from its source (which is sometimes done in an eddy current) and fed to the mouthpiece for inhaling.